Bonding Rigid Nipple

[infinity]

This gem I saw the other day, missing two locknuts.

 

[kwired]

Admittedly I'm somewhat grasping at straws to keep from using 90.4 (I hate using that) but,
with only one locknut securing the nipple to the cabinet(s), I think a case may be made for:

All connections, joints, and fittings shall be made tight using suitable tools.

I'm still researching to find documentation so I can show this part applicable:

using fittings for joints and terminations approved for use with the type raceway
or cable used. (I hope I find a document calling for a locknut inside and out as 250.92 does)It's a bit of a moot point as the electrician has agreed to use bonding bushings but I prefer he do so because the Code requires it not the old inspector.

IMO locknut inside and outside on just one end is good enough to bond the nipple.

 

[jaggedben]

Maybe there's something in UL that speaks to rigid fittings.

Personally I think it's very clear that the guy didn't make a bonding connection at either end. Let's say he had done it with EMT set screw fittings with locknuts, but he forgot to tighten the set screws. The EMT is 'not going anywhere' but without the set screws tightened it's not properly bonded. I agree the word 'tight' is key. In fact, augie, I gotta ask: in the installation in question, was it not possible to firmly grab the nipple by hand and rotate it?

 

[augie47]

IMO locknut inside and outside on just one end is good enough to bond the nipple.

Agree, but he didn't have double locknuts at either enc.

Maybe there's something in UL that speaks to rigid fittings.

Personally I think it's very clear that the guy didn't make a bonding connection at either end. Let's say he had done it with EMT set screw fittings with locknuts, but he forgot to tighten the set screws. The EMT is 'not going anywhere' but without the set screws tightened it's not properly bonded. I agree the word 'tight' is key. In fact, augie, I gotta ask: in the installation in question, was it not possible to firmly grab the nipple by hand and rotate it?

I didn't try but I'd say it was too close to the wall on the back side for me to get a grip.

 

[LarryFine]

This gem I saw the other day, missing two locknuts.

View attachment 21858

I did something slightly similar several years ago. I added a sub-panel to an existing panel in a garage that was drywalled. I mounted the new panel so the lower large KO on the side of the new panel lined up the lower large KO on the side of the old panel, drilled through the stud between them, and inserted a nipple with locknuts only inside both panels. The nipple was not the EGC between panels, though; I added an EGC.

 

[augie47]

I did something slightly similar several years ago. I added a sub-panel to an existing panel in a garage that was drywalled. I mounted the new panel so the lower large KO on the side of the new panel lined up the lower large KO on the side of the old panel, drilled through the stud between them, and inserted a nipple with locknuts only inside both panels. The nipple was not the EGC between panels, though; I added an EGC.

I understand the nipple not being used as a EGC but I would still want a bond bushing to assure the nipple itself had an adequate ground path.

 

[electrofelon]

The nipple was not the EGC between panels, though; I added an EGC.

I understand the nipple not being used as a EGC but I would still want a bond bushing to assure the nipple itself had an adequate ground path.

Does the code anywhere require a different/better method depending on whether or not there is a wire egc installed? I don't think there is, although I admit sometimes I hold fittings without a wire egc to a higher standard.

 

[kwired]

Does the code anywhere require a different/better method depending on whether or not there is a wire egc installed? I don't think there is, although I admit sometimes I hold fittings without a wire egc to a higher standard.

Metallic raceways, fittings, enclosures, must be bonded even if there is multiple EGC pathways.

Secure bonding something like has been discussed here on just one end of a nipple is sufficient to bond the nipple, the second enclosure in such instance would need a wire EGC/bonding jumper since it does not have secure bonding via the supplying raceway. You can't leave said nipple loose fitting on both ends, unless a bonding bushing were used on at least one end and of course bonding jumper installed to that bushing.

 

[LarryFine]

You can't leave said nipple loose fitting on both ends, unless a bonding bushing were used on at least one end and of course bonding jumper installed to that bushing.

I can assure you that the two locknuts mentioned in my case were tightened enough to scrape paint on both sides, with the stud maintaining 1.5" space, but I did not bond it directly.

Question:
Since I used a wire EGC to bond the sub-panel, what prevents considering the nipple to be considered an independent sleeve? The fact that it is in contact with a metallic panel?

If the argument is that it is in contact with the panel, can one then argue it's still not bonded?

 

[infinity]

I can assure you that the two locknuts mentioned in my case were tightened enough to scrape paint on both sides, with the stud maintaining 1.5" space, but I did not bond it directly.

Question:
Since I used a wire EGC to bond the sub-panel, what prevents considering the nipple to be considered an independent sleeve? The fact that it is in contact with a metallic panel?

If the argument is that it is in contact with the panel, can one then argue it's still not bonded?

You cannot run insulated conductors through a sleeve so you cannot just call it a sleeve. The real question is where in the NEC does it say that RMC must be fastened with two locknuts when a wire type EBC is used.

 

[romex jockey]

The real question is where in the NEC does it say that RMC must be fastened with two locknuts when a wire type EBC is used.

i can recall back when we used drywall screws to fasten EGC's to metal boxes, as well as simply twisting EGC's together

sometime back when the term 'mechanically bonded' debuted , y'all know the rest of the story....


~RJ~

 

[lordofthisworld]

Where in the Code does it require a nipple be bonded to an enclosure by a locknut outside the enclosure with a locknut or malleable bushing inside ?

(I have a nipple being used as the ground path between two enclosures with a single locknut inside each enclosure)

(excluding then use of a bond bushing in this case)

I want to say if the voltage is 250V or higher, u need 4 locknuts on a nipple, 1 inside and 1 outside on both ends, (250-97 (2) ), What type of conduit? EMT u can get away with using fittings with a should that sits firmly against the enclosure.

 

[kwired]

I want to say if the voltage is 250V or higher, u need 4 locknuts on a nipple, 1 inside and 1 outside on both ends, (250-97 (2) ), What type of conduit? EMT u can get away with using fittings with a should that sits firmly against the enclosure.

The nipple is bonded with one proper connection regardless of voltage. In order for the nipple to become the EGC between the enclosures it must have a proper connection at both ends, but if you ran a wire EGC through the nipple then you only need one (proper) bond to the nipple and can be at any point.

 

[sameguy]

Sorry I just can't get past the header, that time of the year!

 

[al hildenbrand]

Admittedly I'm somewhat grasping at straws to keep from using 90.4 (I hate using that) but,
with only one locknut securing the nipple to the cabinet(s), I think a case may be made for:

All connections, joints, and fittings shall be made tight using suitable tools.

I'm still researching to find documentation so I can show this part applicable:

using fittings for joints and terminations approved for use with the type raceway
or cable used. (I hope I find a document calling for a locknut inside and out as 250.92 does)It's a bit of a moot point as the electrician has agreed to use bonding bushings but I prefer he do so because the Code requires it not the old inspector.

Boy Howdy. What a surprisingly complicated question.

Back in the mists of memory I recall with certainty that there has to be a locknut on the outside of the box for threaded raceway bonding to a metal box. . . but, running around in the 2017 NEC yielded nothing. I finally got to 1971 NFPA NEC Handbook and Article 370, which, back then, was "Outlet, Switch and Junction Boxes, Fittings." There I found 1971 NEC 370-7:

1971 NEC 370-7. Conductors Entering Boxes or Fittings.
(b) Metal Boxes and Fittings.[/B] . . . last sentence . . . Where raceway or cable is installed with metal outlet boxes or fittings, the conduit shall be secured to such boxes or fittings.

In the 2017 NEC, this can be found as the last sentence of 314.17(B).

And, again going back to the 1971:

1971 NEC
Article 373 Cabinets and Cutout Boxes
373-6. Deflection of Conductors.
(b) Insulation at Bushings. . . . last sentence . . . Where conduit bushings are constructed wholly of insulating material, a locknut shall be installed both inside and outside the enclosure to which the conduit is attached.

To my knowledge, 1971 NEC 373-6(b) did not survive the transitions to 2017 NEC 300.4(G).

 

[Greentagger]

I too had a hard time accepting a lock nut on outside and bushing on inside was compliant . Reading 250.92(B) , it definitely makes reference to “ standard lock nuts or bushings shall not be .....................but shall be permitted to be installed to make a mechanical connection...........”. I guess technically the bushing would have to be listed for that purpose. I know this horse has been beat to death through the years.

 

[Little Bill]

2 year old thread